This invention relates generally to a new and improved tool for enlarging well bores. More particularly, this invention concerns a novel well bore enlarger utilizing synthetic diamond cutting technology.
In the past, it has been common to use tools to open or to underream well bores. Most such tools utilize roller cone-type cutters which are not as effective in cutting through many sedimentary formations as are tools using synthetic diamond material. The cone-type cutters may also have moving parts, such as cones and bearings, which may break off during use and fall into the well bore.
In the past, such expandable-arm tools have been built to create a neutral turning moment or inward turning moment about the hinged mechanism securing the cutting arms to the tool. This was done because the mechanism stopping the expansion of the cutting arm was not strong enough to support outward turning moments. To support the inward turning moment, such tools had to be provided with a locking mechanism behind the cutting arm to lock the arm in its open position. Locking mechanisms are not always reliable and, if the cutting arm fails to close, the tool cannot be brought to the surface if it has passed through a restriction in the well bore while in the closed position, i.e., if only the lower part of the well bore has been enlarged. An expensive fishing operation is then required to recover the tool, which, if unsuccessful, could mean abandonment of the well.
Attempts have been made to adapt previous tools for use with synthetic diamond cutting technology. these attempts have failed because of the lack of strength and stability of previous tools and because of the inability of previous tools to provide adequate cleaning and cooling of the synthetic diamond cutting surfaces. Synthetic diamond material cannot tolerate high levels of vibration or shock loading. In order to efficiently cut through a formation, the synthetic diamond cutting surfaces must be well cleaned. Additionally, the synthetic diamond material will debraze and break down if not properly cooled during cutting.
Attempts have been made to provide solutions to the problems which arise in using synthetic diamond cutting surfaces in well bore enlarging tools, such as U.S. Pat. No. 4,431,065 to Andrews which addresses the necessity for cooling and cleaning the cutting surfaces. The tool disclosed in Andrews suffers from a number of disadvantages. The geometric configuration of the cutting arm is such that fluid does not flow directly toward the cutting surface when the arm is fully extended, thus lessening the cooling and cleaning effect. Andrews does not disclose the ability to fit interchangeable nozzles to create optimum hydraulics at the cutting faces and below the tool. The problems of vibration and shock loading are not addressed by Andrews.
The need exists for a tool which can utilize synthetic diamond cutting technology and which overcomes the problems inherent in the use of such technology. The present well bore enlarger addresses and solves such problems.